In paper forms the specific sub-questions cannot be hidden from the user when they are not relevant to them - but in interactive forms this is relatively easy to do. Use progressive revealing as much as possible in your form design to shield your users from questions they do not need to see.

Customise response boxes to reflect required answers and reduce completion errors. If asking for a persons date of birth, it makes sense to provide a box with the exact number of required digits and an example or guidance note to explain the format that the date should be entered in (DD/MM/YYYY).